Centring on an ordinary man with extraordinary determination, Tomáš Kratochvíl’s documentary shows how one simple video can ignite a revolutionary movement. After emigrating to the UK nearly 15 years ago, Czech Roma lorry driver Štefan Pongo built a new life for himself and his family in Manchester. At the same time, the persecution faced by his community never strayed far from Pongo’s mind. After hearing a speech in which Miloš Zeman, then the president of the Czech Republic, claimed that 90% of the Roma people were “socially unadaptable” and resistant to work, Pongo started a viral appeal online where he and countless other Roma compatriots posted selfies of themselves at their workplaces.

The appeal was straightforward, yet hugely impactful. Its aim was to battle harmful stereotypes thrust upon Roma people, which Pongo himself had experienced first-hand from a young age. In one particularly painful anecdote, he mentioned his primary school teacher rubbing his arms in front of the whole class to demonstrate how “dirty” the Roma are. As Pongo took a leadership role in the fight for Romani rights, his activism also translated into real-world actions, organising protest rallies in Brussels, and travelling to rural Slovenia to deliver aid to the most vulnerable in the community.

By juxtaposing Pongo’s virtual livestreams with his in-person trips, Kratochvíl’s documentary keenly demonstrates how activism can take many shapes and forms. The film also doesn’t shy away from how the desire to make changes can also create a mental rabbit hole as Pongo’s wife laments the excessive time that he spends at the computer, occasionally at the neglect of his own family. It is this inclusion of the bad with the good that makes Pongo Calling a nuanced gem, and the sudden tragedy that bookends the film even more heartbreaking.

• Pongo Calling is on True Story from 21 June.